Organic EL Device Using Asymmetric Anthracene Hosts for White Emission
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Solution Overview
Problem
Current organic EL devices face challenges in achieving high luminous efficiency and long device lifetime for mixed-color emission, particularly in obtaining balanced white emission due to the low luminous efficiency of fluorescent blue emission and accelerated degradation of fluorescent-emitting layers when trying to enhance exciton generation.
Innovation Solution
An organic EL device structure incorporating a phosphorescent-emitting layer with a phosphorescent host and dopant, and a fluorescent-emitting layer with specific asymmetric anthracene or pyrene derivatives as hosts, which enhances external quantum efficiency and prolongs device lifetime by optimizing exciton generation and reducing material load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If exciton generation in the fluorescent-emitting layer is increased to enhance blue emission luminance, then the luminance of blue emission is improved, but the load on the fluorescent-emitting layer increases and material degradation is accelerated, shortening device lifetime
Solution Approach 1:
The device is divided into two separate emitting layers: a phosphorescent-emitting layer for green-to-red emission and a fluorescent-emitting layer for blue emission. This segmentation allows each layer to be optimized independently, with the phosphorescent layer handling the majority of luminance generation efficiently, thereby reducing the exciton generation load on the fluorescent layer and slowing material degradation.
Solution Approach 2:
The patent employs specific asymmetric anthracene derivatives or pyrene derivatives as fluorescent hosts with optimized molecular structures and substituents. These parameter changes in molecular structure improve the luminous efficiency of the fluorescent layer, allowing adequate blue emission without requiring excessive exciton generation that would accelerate degradation.
2Use of energy by moving object
If phosphorescent materials are used for long-wavelength emission to achieve high quantum efficiency, then the quantum efficiency of phosphorescent emission is improved, but the inability to provide short-wavelength emission prevents balanced mixed-color emission
Solution Approach 1:
The patent merges phosphorescent emission (for green-to-red wavelengths with high quantum efficiency) and fluorescent emission (for blue wavelengths) into a single device structure. This combination allows the device to achieve both high overall quantum efficiency from the phosphorescent layer and the necessary short-wavelength blue emission from the fluorescent layer, enabling balanced white light emission.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed device achieves high luminous efficiency and extended lifetime by balancing the emission colors and reducing material degradation, effectively addressing the limitations of previous technologies.
Implementation Method 1
a phosphorescent-emitting layer containing a phosphorescent host and a phosphorescent dopant for phosphorescent emission
Implementation Method 2
a fluorescent-emitting layer containing a fluorescent host and a fluorescent dopant for fluorescent emission
Implementation Method 3
an anode for injecting holes
Implementation Method 4
a cathode for injecting electrons
Data Source
AI summary
An organic EL device includes: an anode for injecting holes; a phosphorescent-emitting layer; a fluorescent-emitting layer; and a cathode for injecting electrons. The phosphorescent-emitting layer contains a phosphorescent host and a phosphorescent dopant for phosphorescent emission. The fluorescent-emitting layer contains a fluorescent host and a fluorescent dopant for fluorescent emission. The fluorescent host is at least one of an asymmetric anthracene derivative represented by a formula (1) below and a pyrene derivative represented by a formula (2) below.